1. Field of the Invention
The present invention concerns extracorporeal treatment of blood by dialysis. More particularly, the present invention is directed to a method for checking the operation of sensors situated in a dialysis liquid circuit of an artificial kidney.
2. Description of the Related Act
In a dialysis liquid circuit of an artificial kidney there are many sensors making it possible to measure or check a certain number of characteristics of the dialysis liquid, such, as for example, the conductivity or concentration of salts. Such characteristics are useful to know and to monitor in the course of a treatment session since the efficiency of the blood purification depends on the composition of the dialysis liquid used. In addition, it is possible in certain cases to deduce the value of certain characteristics of the blood by means of measurements carried out on the dialysis liquid.
In particular, one may determine the concentration of sodium in the blood circulating on the other side of a membrane based on measurements of the conductivity of the dialysis liquid, which avoids the need for taking blood samples from the patient. The measurement of the conductivity may be carried out by recirculating dialysis liquid in a part of the blood circuit, until an equilibrium with the blood is obtained, as described in the article "Optimization of Sodium Concentration by Plasma Water Conductivity Monitoring" by Petitclerc, Man, Goureau, Jehenne and Funck-Brentano (Progress in Artificial Organs--1985). Alternatively and more advantageously, conductivity may be measured by means of two measurements effected respectively upstream and downstream from the device used for the blood treatment. The two measurements may even be obtained, if required, by means of a single conductivity meter alternately washed by the fresh dialysis liquid and by the used dialysis liquid. The natraemia determinations thus effected may subsequently be used to determine the composition of the most favorable dialysis liquid according to the purification desired. Hence, it is very important that the data provided by the conductivity meter are reliable. The conventional means for checking the operation of the conductivity meters usually necessitates a considerable period of downtime for the artificial kidney, which reduces the time available for patient treatment.